An example of the radiation detector used in a CT sensor or the like is a detector of a configuration wherein a scintillator is installed on a light-incident surface of a semiconductor photodetecting element. In the radiation detector of this configuration, scintillation light is generated with incidence of radiation, such as X-rays, γ-rays, or a charged particle beam, as an object to be detected, into the scintillator. Then the semiconductor photodetecting element detects the incident scintillation light from the scintillator to output the electrical signal corresponding to the intensity of the radiation.
A signal processing element is provided in order to perform signal processing of the electrical signal outputted from the semiconductor photodetecting element. In this connection, a semiconductor device is constructed in one united body by connecting a semiconductor element to a wiring substrate with a conduction path, as one of configurations for establishing electric connection between the semiconductor element and the signal processing element to transmit the electrical signal, and the signal processing element is arranged to be connected to the wiring substrate of this semiconductor device. Such semiconductor device using the wiring substrate is used in various applications other than the radiation detector (e.g., reference is made to Japanese Patent No. 2555720 and Japanese Patent Application Laid-Open No. H3-203341).